Beam irradiation apparatus

ABSTRACT

An attachment lens is arranged in a stage subsequent to a scanning lens. After a laser beam is converged by the scanning lens, the laser beam is converted into a parallel beam by the attachment lens. When the scanning lens is displaced in a direction perpendicular to an optical axis of the laser beam, a traveling direction of the laser beam is bent by a predetermined angle immediately after the laser beam passes through the scanning lens. Then, the traveling direction of the laser beam is further bent by a predetermined angle in the same direction by the passage of the laser beam through the attachment lens. Accordingly, a final swing angle of the laser beam outgoing from an outgoing window is increased by a swing angle imparted by the attachment lens compared with the case where the attachment lens is not arranged. One of lens surfaces of the attachment lens is formed in a toroidal surface, which allows the laser beam to have a long outline in a vertical direction.

This application claims priority under 35 U.S.C. Section 119 of JapanesePatent Application No. 2006-041924 filed Feb. 20, 2006 and JapanesePatent Application No. 2006-058578 filed Mar. 3, 2006.

RELATED PATENT APPLICATIONS

This is a divisional of U.S. patent application Ser. No. 11/675,852,filed Feb. 26, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a beam irradiation apparatus which issuitably used in an inter-vehicle distance detector, a distancedetector, and the like.

2. Description of the Related Art

Recently, a detection apparatus in which a target region is irradiatedwith a laser beam to detect an obstacle within the target region ismounted on a passenger automobile. In such a detection apparatus, thelaser beam is scanned in a horizontal direction and a vertical directionwithin the target region, and a distance between the automobile and theobstacle is detected from an acceptance state of the reflected light.

In order to scan the laser beam, a so-called beam irradiation apparatusis arranged in the detection apparatus. For example, a lens actuatordisclosed in Japanese Patent Publication Laid-Open No. 11-83988 can beused to scan the laser beam. In the actuator, a scanning lens convertsthe laser beam (diffuse light) emitted from a light source into aparallel beam or a light beam slightly diffused rather than the parallelbeam. The scanning lens is two-dimensionally driven in a directionperpendicular to an optical axis of the laser beam according to thedrive of the actuator, which allows the laser beam to be scanned withinthe target region.

However, in the conventional technique, there is generated a problem aswing width of the laser beam is restricted by a drive amount of theactuator. Because the drive amount of the actuator has a predeterminedrestriction, in order to displace the scanning lens beyond therestriction, it is necessary to enlarge the actuator, or it is necessaryto enhance drive force of an electromagnetic circuit including a magnetand a coil. However, the beam irradiation apparatus is thereforeenlarged to generate a further problem that power consumption isincreased.

In the conventional beam irradiation apparatus, generally the targetregion is divided into matrixes in the horizontal direction and thevertical direction, an outgoing level of the laser beam is enhanced in apulsating manner at timing a scanning position of the laser beam reacheseach grid position, and the grid position is irradiated with the laserbeam. The detection whether or not the obstacle exists at the gridposition is performed based on whether or not the light reflected fromthe target region is detected at each grid position, and a distance tothe obstacle is detected based on a time difference between outgoingtiming and acceptance timing of the laser beam.

In this case, resolution of the grid has an influence on accuracy of theobstacle detection. That is, as the resolution of the grid is enhanced,the accuracy of the obstacle detection is enhanced in the target region.At the same time, when the resolution of the grid is enhanced, anoutgoing frequency of the laser beam is increased, which complicatesscanning control. On the other hand, in the passenger automobile it isnecessary that the detection accuracy in the horizontal direction beenhanced rather than the detection accuracy in the vertical direction.Accordingly, it is desirable that the resolution of the grid be enhancedin the horizontal direction while lowered in the vertical direction.

SUMMARY OF THE INVENTION

In view of the foregoing, a first object of the invention is to providea beam irradiation apparatus which can increase the swing width of thelaser beam with a simple configuration while a displacement amount ofthe scanning lens is suppressed to a small level. A second object of theinvention is to provide a beam irradiation apparatus which can irradiatethe laser beam having a proper outline according to the resolution ofthe grid.

A beam irradiation apparatus according to a first aspect of theinvention realizes the first object, by including a light source whichemits a laser beam; a scanning unit which displaces a travelingdirection of the laser beam emitted from the light source toward adirection perpendicular to an optical axis of the laser beam; and a lenselement which imparts wide angle action to a swing angle of the opticalaxis, the swing angle being generated by the scanning unit.

In the beam irradiation apparatus according to the first aspect of theinvention, the scanning unit may be configured to displace the laserbeam in a first direction and a second direction, the first directionbeing perpendicular to the optical axis, and the second direction beingperpendicular to both the first direction and the optical axis, and thelens element may be configured to impart the wide angle action to thelaser beam in at least one of the first direction and the seconddirection.

According to the beam irradiation apparatus of the first aspect, theswing width in scanning the laser beam can be increased by the wideangle action imparted by the lens element.

The beam irradiation apparatus according to the first aspect of theinvention is implemented by the following first embodiment. In theembodiment, the scanning unit in the first aspect corresponds to ascanning lens 301 and lens actuator 300 or a polygon mirror 900, and thelens element in the first aspect corresponds to an attachment lens 700.

A beam irradiation apparatus according to a second aspect of theinvention realizes the first object by including a light source whichemits a laser beam; a first lens which displaces a traveling directionof the laser beam emitted from the light source toward a directionperpendicular to an optical axis of the laser beam; an actuator whichdrives the first lens; and a second lens which imparts wide angle actionto a swing angle of the optical axis, the swing angle being generated bydisplacing the first lens.

In the beam irradiation apparatus according to the second aspect of theinvention, the first lens may be configured to converge the laser beamsmaller than a parallel beam, and the second lens may be configured todiffuse the laser beam converged by the first lens into a substantiallyparallel state.

In the beam irradiation apparatus according to the second aspect of theinvention, the actuator may be configured to two-dimensionally drive thefirst lens in a first direction and a second direction, the firstdirection being perpendicular to the optical axis of the laser beam, andthe second direction being perpendicular to both the first direction andthe optical axis, and the second lens may be configured to impart thewide angle action to the laser beam in at least one of the firstdirection and the second direction.

According to the beam irradiation apparatus of the second aspect, theswing width in scanning the laser beam can be increased by the wideangle action imparted by the second lens. For example, in a case where abeam diameter (by ray tracing) of the laser beam outgoing from thesecond lens is 1/n times the beam diameter (also by ray tracing)incident to the first lens while the laser beam outgoing from the secondlens is the parallel beam, scanning can be performed with the laser beamhaving the swing width n times that of a case where the second lens isnot used.

The beam irradiation apparatus according to the second aspect of theinvention is implemented by the following second embodiment. In theembodiment, the first lens in the second aspect corresponds to thescanning lens 301, the actuator in the second aspect corresponds to thelens actuator 300 or the polygon mirror 900, and the second lens in thesecond aspect corresponds to the attachment lens 700.

A beam irradiation apparatus according to a third aspect of theinvention realizes the second object by including a light source whichemits a laser beam; a scanning unit which scans the laser beam emittedfrom the light source within a target region; and an optical memberwhich deforms an outline of the laser beam in the target region so as tobecome thin in one direction.

In the beam irradiation apparatus according to the third aspect of theinvention, the scanning unit may be configured to scan the laser beam inat least a horizontal direction within the target region, and theoptical member may be configured to deform the outline of the laser beamin the target region so as to become thin in a direction perpendicularto the horizontal direction.

According to the beam irradiation apparatus of the third aspect, theoutline of the laser beam on the target region is adjusted so as tobecome thin in one direction by the optical action imparted by theoptical member. Accordingly, as described above, the target region canbe irradiated with the laser beam having the outline suitable to thegrid shape, even if the resolution of the grid set in the target regionis changed. Therefore, the beam irradiation apparatus according to thethird aspect of the invention can efficiently and stably realize thescanning operation.

The beam irradiation apparatus according to the third aspect of theinvention is implemented by the following second embodiment. In theembodiment, the scanning unit in the third aspect corresponds to thescanning lens 301 and the lens actuator 300 or the polygon mirror 900,and the optical member in the third aspect corresponds to the attachmentlens 700.

However, the invention is illustrated by the following embodiments onlyby way of example, and the invention is not limited to the embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and novel features of the invention will become apparentfrom the following description of embodiments with reference to theaccompanying drawings in which:

FIG. 1 shows a configuration of a beam irradiation apparatus accordingto a first embodiment of the invention;

FIG. 2 shows a configuration of a lens actuator in the first embodiment;

FIGS. 3A and 3B show simulation results of behaviors in which anirradiation laser beam and a separated beam are swung respectively whena scanning lens 301 is displaced in one direction in the firstembodiment;

FIG. 4 shows a structure of a PSD of the first embodiment;

FIGS. 5A and 5B show the structure and a voltage characteristic of thePSD in the first embodiment respectively;

FIG. 6 shows a relationship between a movement amount of a scanning lensand a scanning angle in the first embodiment;

FIGS. 7A to 7F show an intensity distribution of a laser beam when anirradiation laser beam in the first embodiment is displaced;

FIGS. 8A to 8F show the intensity distribution of the laser beam whenthe irradiation laser beam in the first embodiment is displaced;

FIGS. 9A to 9C show the intensity distribution of the laser beam whenthe irradiation laser beam in the first embodiment is displaced;

FIGS. 10A to 10F show the intensity distribution of the laser beam whenthe irradiation laser beam in a second embodiment is displaced;

FIGS. 11A to 11F show the intensity distribution of the laser beam whenthe irradiation laser beam in the second embodiment is displaced;

FIGS. 12A to 12C show the intensity distribution of the laser beam whenthe irradiation laser beam in the second embodiment is displaced;

FIGS. 13A and 13B show examples of a scanning orbit and a state of theirradiation laser beam in the second embodiment; and

FIG. 14 shows a configuration of a beam irradiation apparatus accordingto a modification.

However, these drawings are used only for the description of specificembodiments by way of example, and the invention is not limited to thedrawings.

DESCRIPTION OF PREFERRED EMBODIMENTS

Preferred embodiments of the invention will be described below withreference to the drawings.

First Embodiment

FIG. 1 shows a configuration of a beam irradiation apparatus accordingto a first embodiment of the invention. FIG. 1 shows only a head portion(beam irradiation head) of the beam irradiation apparatus, and aconfiguration of a control circuit is neglected in FIG. 1.

The beam irradiation head includes a semiconductor laser 100, anaperture 200, a lens actuator 300, a beam splitter 400, a servo lens500, a PSD (Position Sensitive Detector) 600, an attachment lens 700,and an outgoing window 800.

The laser beam emitted from the semiconductor laser 100 is shaped in adesired shape by the aperture 200, and the laser beam is incident to ascanning lens 301. The scanning lens 301 includes a convex lens havingaspheric surfaces, and the scanning lens 301 forms the laser beamincident from the semiconductor laser 100 into the convergent beamsmaller than a parallel beam. The scanning lens 301 is supported by alens actuator 300 so as to be able to be displaced in a Y-Z plane ofFIG. 1. In the laser beam which passes already through the scanning lens301, an output angle is changed in the Y-Z plane according to drive ofthe lens actuator 300. The scanning lens 301 is adjusted by the lensactuator 300 such that a center axis of the scanning lens 301 is alignedwith a center axis of the attachment lens 700 when the scanning lens 301is located at a neutral position.

A part of the laser beam is reflected and separated from the laser beam(hereinafter referred to as “irradiation laser beam”), with which atarget region is irradiated, by the beam splitter 400 after the laserbeam passes through the scanning lens 301. The separated laser beam(hereinafter referred to as “separated beam”) is converged on the PSD600 through the servo lens (convergent lens) 500.

The PSD 600 has an acceptance surface parallel to an X-Y plane of FIG.1, and the PSD 600 outputs a current according to a convergent positionof the separated beam on the acceptance surface. At this point, theconvergent position of the separated beam on the acceptance surfacecorresponds one-on-one to an irradiation position of the irradiationlaser beam on the target region. Therefore, the output current from thePSD 600 corresponds to the irradiation position of the irradiation laserbeam on the target region.

A signal processing circuit (not shown) processes the current signal,and the irradiation position of the irradiation laser beam. The scanningof the irradiation laser beam is controlled based on the detectionresult. The configuration and the current output operation of the PSD600 will be described later with reference to FIGS. 4, 5A and 5B.

The irradiation laser beam passing through the beam splitter 400 isincident to the attachment lens 700. The attachment lens 700 includes aconcave lens which imparts diffusion action to the laser beam in anall-around direction. The attachment lens 700 converts the irradiationlaser beam, which is inputted as the convergent beam, into the parallelbeam. The irradiation laser beam converted into the parallel beam by theattachment lens 700 passes through the outgoing window 800, and thetarget region is irradiated with the irradiation laser beam.

FIG. 2 shows a configuration (exploded perspective view) of the lensactuator 300.

Referring to FIG. 2, the scanning lens 301 is placed in an opening of acentral portion of a lens holder 302. Coils are attached to for sidefaces of the lens holder 302 respectively, and a projection portion inthe center of a yoke 303 is into each coil from each arrow direction.Tongue pieces on both sides of each yoke 303 are fitted in recesses of apair of yoke fixing members 305. A magnet 304 is fixed to each yokefixing member 305 such that the tongue piece of the yoke 303 issandwiched between the magnet 304 and the yoke fixing member 305. Inthis state of things, the yoke fixing member 305 is attached to a base(not shown) along with the magnet 304.

A pair of wire fixing members 306 is also attached to the base toelastically support the lens holder 302 through wires 307. Holes throughwhich the wires 307 are fitted respectively are made in four corners ofthe lens holder 302. After the wire 307 is fitted through the hole, bothends of the wire 307 are fixed the wire fixing members 306 respectively.Therefore, the wire fixing member 306 elastically supports the lensholder 302 through the wires 307.

In driving the lens actuator 300, an actuator drive circuit suppliesdrive signals to the coils attached to the lens holder 302, whichgenerates electromagnetic force to two-dimensionally drive the scanninglens 301 along with the lens holder.

FIG. 3A shows a simulation result performed by ray tracing for abehavior in which the irradiation laser beam is swung when the scanninglens 301 is displaced in a direction of an arrow A. FIG. 3B shows asimulation result performed by the ray tracing for a behavior in whichthe separated beam is swung when the scanning lens 301 is displaced inthe same direction (direction of the arrow A). FIG. 3B shows only atrajectory of the laser beam incident to the servo lens 500.

As shown in FIG. 3A, a traveling direction of the irradiation laser beamis bent by a predetermined angle immediately after the irradiation laserbeam passes through the scanning lens by displacing the scanning lens301. Then, the irradiation laser beam passes through the attachment lens700, which further bends the traveling direction by a predeterminedangle toward the same direction. Accordingly, the final swing angle ofthe irradiation laser beam outgoing from the outgoing window 800 becomeslarger by the swing angle imparted by the attachment lens 700 whencompared with the case where the attachment lens 700 is not arranged.Because the attachment lens 700 includes the concave lens which impartsthe diffusion action to the laser beam in the all-around direction, theswing-angle increased effect (wide angle action) is also generated inthe all-around direction of the attachment lens 700. The swing-angleincreased effect (wide angle action) will be described later withreference to FIG. 6.

FIG. 4 shows the structure of the PSD 600. FIG. 4 shows the structure ofthe PSD 600 when viewed from the Y-axis direction of FIG. 1.

As shown in FIG. 4, the PSD 600 has a structure in which a P-typeresistance layer is formed on a surface of an N-type high-resistancesilicon substrate. The P-type resistance layer acts as both theacceptance surface and the resistance layer. Electrodes X1 and X2 andelectrodes Y1 and Y2 (not shown in FIG. 4) are formed on the surface ofthe resistance layer. The electrodes X1 and X2 output a photocurrent inthe X-direction of FIG. 1, and the electrodes Y1 and Y2 output aphotocurrent in the Y-direction of FIG. 1. A common electrode is formedin the backside.

When the separated beam is converged onto the acceptance surface, acharge is generated at the convergent position according to alightquantity. The charge in the form of the photocurrent reaches theresistance layer, and the charge is divided in inverse proportion to adistance to each of the electrodes X1, X2, Y1, and Y2 and delivered fromthe electrodes. Each of the currents delivered from the electrodes X1,X2, Y1, and Y2 has a magnitude divided in inverse proportion to thedistance to each electrode from the convergent position of the separatedbeam. Therefore, the convergent position can be detected on theacceptance surface based on the currents delivered from the electrodesX1, X2, Y1, and Y2.

FIG. 5A shows the effective acceptance surface of the PSD 600. FIG. 5Bshows a relationship between the separated-beam convergent position onthe effective acceptance surface and a position detection voltage whichis generated by a PSD signal processing circuit based on the currentsobtained from the electrodes X1, X2, Y1, and Y2. In FIG. 5A, theeffective acceptance surface is formed in a square shape. FIG. 5B showsthe relationship between an output voltage and displacement amount inthe X-direction and Y-direction of the convergent position with respectto a reference position while a center position on the effectiveacceptance surface is set to the reference position (zero position).

The signal processing circuit generates a voltage Xout corresponding tothe displacement amount in the X-direction of the convergent positionand a voltage Yout corresponding to the displacement amount in theY-direction based on the currents delivered from the electrodes X1, X2,Y1, and Y2, and the signal processing circuit outputs the voltages Xoutand Yout to a DSP (Digital Signal Processor) control circuit through anADC (Analog Digital Converter). The DSP control circuit detects thedisplacement amounts in the X-direction and Y-direction of theconvergent position from the inputted voltages Xout and Yout.

FIG. 6 shows a result in which a relationship between a movement amountof the scanning lens 301 and a scanning angle of the irradiation laserbeam is simulated under constant conditions in the configuration ofFIG. 1. The scanning angle of a vertical axis is one which is formedbetween the optical axis of the laser beam emitted from thesemiconductor laser 100 and the optical axis of the laser beam outgoingfrom the outgoing window 800. FIG. 6 also shows a relationship betweenthe movement amount of scanning lens 301 and the scanning angle when theattachment lens 700 is neglected as a comparative example.

The simulation conditions are as follows.

(Scanning Lens 301)

-   -   double-aspheric surface    -   focal distance: 13.4912 mm    -   effective diameter: φ16 mm (aperture)    -   center thickness: 5 mm    -   refractive index: 1.517

(Attachment Lens 700)

-   -   incident side: spherical surface/    -   outgoing side: spherical surface    -   focal distance: −23.0474 mm    -   effective diameter: φ14.0 mm    -   center thickness: 1 mm    -   refractive index: 1.517

(Other)

-   -   distance between semiconductor laser and attachment lens: 52.81        mm    -   displacement amount of scanning lens: ±2 mm

It is assumed that the scanning lens 301 and the attachment lens 700 arearranged at the positions where the laser beam outgoing from theattachment lens 700 becomes the parallel beam and the beam diameter (bythe ray tracing) outgoing from the attachment lens 700 becomes a half ofthe beam diameter (by the ray tracing) incident to the scanning lens 301when the center axes of the scanning lens 301 and attachment lens 700are aligned with each other, namely, when the scanning lens 301 islocated at the neutral position.

As shown in FIG. 6, when the above-described design example (simulationconditions) is adopted, the double scanning angle can be obtained ateach scanning lens position compared with the comparative example. Thatis, according to the design example, even if the scanning lens 301 isdisplaced lesser, the scanning can be performed with the irradiationlaser beam having the large swing angle.

Each lens suitable to the simulation conditions can be formed based onthe following lens data.

(Scanning Lens 301)

a. Incidence Plane (Aspheric Surface)

curvature radius 16.8777649771835 mm

aspherical coefficient (aspheric surface generation polynomial):

conical constant (K) −8.48832199279343 fourth-order coefficient (A)−4.27096033316007e−007 sixth-order coefficient (B)  1.17521904684828e−006 eighth-order coefficient (C) −2.111559547426e−008b. Outgoing Plane (Aspheric Surface)

curvature radius −10.4603963534906 mm

aspherical coefficient (aspheric surface generation polynomial):

conical constant (K) 0.0947470811575341 fourth-order coefficient (A)   7.4254388113816e−005 sixth-order coefficient (B)  2.33700944147862e−006 eighth-order coefficient (C)−1.55061157703029e−008c. Material: glass/BK7 (refractive index=1.517)

(Attachment Lens 701)

a. Incidence Plane (Spherical Surface)

curvature radius −60.3114453703036 mm

b. Outgoing Plane (Spherical Surface)

curvature radius 14.68847686175 mm

c. Distance between Center Surfaces 1 mmd. Material glass/BK7 (refractive index=1.517)

The above simulation is performed on the conditions that, when thescanning lens 301 is located at the neutral position, the laser beamoutgoing from the attachment lens 700 becomes the parallel beam and thebeam diameter (by the ray tracing) outgoing from the attachment lens 700becomes a half of the beam diameter (also by the ray tracing) incidentto the scanning lens 301. However, in the case where conditions are setto the optical system such that a beam diameter (by the ray tracing) ofthe laser beam outgoing from the attachment lens 700 is 1/n times thebeam diameter (also by the ray tracing) incident to the scanning lens301, the scanning can be performed with the irradiation laser beamhaving the swing angle n times that of the comparative example. That is,the smaller is decreased the beam diameter of the laser beam outgoingfrom the attachment lens 700, the larger is increased the swing angle ofthe irradiation laser beam to the displacement amount of the scanninglens 301.

However, when the beam diameter of the laser beam outgoing from theattachment lens 700 is excessively decreased, scattering is generated inthe irradiation laser beam by a water droplet or dust adhering to theoutgoing window 800, which results in a problem that the target regionis not smoothly irradiated with the irradiation laser beam. Accordingly,when the laser beam is incident to the scanning lens 301, it isnecessary that the beam diameter be set to an adequate size inconsideration of both the adverse affect of the water droplet or dustand the swing angle necessary to the scanning of the irradiation laserbeam.

In the case where the simulation conditions are set to the opticalsystem, because the sufficiently large beam diameter is obtained, thetarget region can smoothly be irradiated with the irradiation laser beamwithout generating the adverse affect of the water droplet or dust.

In the first embodiment, when the scanning lens is displaced from theneutral position, aberration is generated according to the differencebetween the center axis of the scanning lens and the optical axis of theincident laser beam. FIGS. 7A to 7F, 8A to 8F, and 9A to 9C showsimulation results in which a generation state (intensity distribution)of the aberration is simulated when the scanning lens 301 is displacedwhile the simulation conditions are set to the optical system. Theintensity distribution shown in FIGS. 7A to 7F, 8A to 8F, and 9A to 9Cis one in the case where the intensity distribution of the irradiationlaser beam is obtained in the target region positioned 100 m away fromthe attachment lens 700.

Each of FIGS. 7A to 7F, 8A to 8F, and 9A to 9C shows a beam intensitydistribution (left) when the irradiation laser beam is swung by apredetermined angle in the horizontal direction while the scanning lensis displaced, a beam profile (middle) in the horizontal direction(horizontal direction of the drawing) with respect to each beamintensity distribution, and a beam profile (right) in the verticaldirection (vertical direction of the drawing). The horizontal axis ofthe beam profile is a distance from the beam center position (where thebeam intensity is the highest), and the vertical axis is an intensitylevel when the maximum intensity is set to 100. In the horizontal axis,the beam center position is set to zero.

As can be seen from FIGS. 7A to 7F, 8A to 8F, and 9A to 9C, in the casewhere the simulation conditions are set to the optical system, thegeneration of the aberration becomes conspicuous from around theposition where the irradiation laser beam is scanned by about 15° fromthe neutral position (see FIGS. 8D to 8F), and the intensitydistribution of the irradiation laser beam becomes distorted in thehorizontal direction. When the scanning angle becomes about 20° (seeFIGS. 9A to 9C), the distortion of the intensity distribution becomessignificant. The distortion is also generated when the irradiation laserbeam is scanned in the vertical direction.

In order to decrease the distortion, it is necessary that the surface ofthe scanning lens 301 or attachment lens 700 be set to be able tosuppress the aberration generated by the displacement of the scanninglens, or it is necessary that a correction lens be separately arrangedin an optical path to suppress the aberration. On the apparatus side inwhich the beam irradiation apparatus of the first embodiment is mounted,when the distortion of the intensity distribution becomes troublesome,it is necessary that the distortion be decreased by suchcountermeasures.

Although the embodiment (first embodiment) of the invention describedabove, the invention is not limited to the first embodiment, but variousmodifications could be made.

In the first embodiment, the attachment lens 700 is formed by theconcave lens which imparts the wide angle action to the laser beam inall-around direction. However, for example, in the attachment lens 700,a lens which imparts the wide angle action to the laser beam only in onedirection may appropriately be arranged in place of the concave lens. Inthis case, in the configuration of FIG. 1, the attachment lens 700 isarranged such that the direction of the wide angle action is alignedwith either the Z-axis direction or the Y-axis direction of FIG. 1.

For example, in the case where the direction of the wide angle action ofthe attachment lens 700 is aligned with the Z-axis direction of FIG. 1,the scanning angle of the irradiation laser beam is amplified by thewide angle action of the attachment lens 700 only when the scanning lens301 is displaced in the Z-axis direction. In this case, even if thescanning lens 301 is displaced in the Y-axis direction, the wide angleaction of the attachment lens 700 has no influence on the scanning angleof the irradiation laser beam, but the scanning angle of the irradiationlaser beam is generated only by the displacement of the scanning lens301.

In such cases, the lens surfaces of the scanning lens 301 may be formedsuch that the laser beam is further converged from the parallel beam inthe Z-axis direction of FIG. 1 while the laser beam is set to theparallel beam in the Y-axis direction of FIG. 1. The lens surfaces ofthe attachment lens 700 may be formed such that the convergent state inthe Z-axis direction which is imparted by the scanning lens is convertedinto the parallel beam. This enables the irradiation laser beam to beset to the parallel beam after the irradiation laser beam passes throughthe attachment lens 700.

The modification is an effective example particularly in the case wherethe large scanning range is ensured in one direction. For example, inthe case where the beam irradiation apparatus is mounted on the vehicle,it is necessary that the large scanning range be set in the horizontaldirection rather than the vertical direction to rapidly detect anobstacle lateral to the vehicle or jump from the side. The modificationis suitable to such situations.

In the modification, because the degree of the change in scanning anglein the Z-axis direction is larger than the degree of the change inscanning angle in the Y-axis direction, it is desirable that theseparated beam converged on the PSD 600 be moved on the acceptancesurface so as to reflect the degree of the change. Accordingly, in themodification, it is desirable that the lens surfaces of the servo lens500 be designed such that the convergent position of the separated beamis moved on the acceptance surface.

Second Embodiment

In configuration of the first embodiment, both the incidence plane andoutgoing plane of the attachment lens 700 are formed in the sphericalsurface, and the uniform diffusion action is imparted to the laser beamin the all-around direction. However, a function of adjusting the beamshape of the irradiation laser beam can be imparted to one of theincidence plane and the outgoing plane. For example, one of theincidence plane and the outgoing plane is formed in a toroidal surface,and the irradiation laser beam can be formed in the beam shape thinnerthan that of the first embodiment.

FIGS. 10A to 10F, 11A to 11F, and 12A to 12C show simulation results inthe case where the incidence plane of the attachment lens 700 is set toa toroidal surface. The intensity distribution of the irradiation laserbeam is simulated when the scanning lens 301 is displaced while thefollowing conditions are set to the optical system. The intensitydistribution shown in FIGS. 10A to 10F, 11A to 11F, and 12A to 12C isone in the case where the intensity distribution of the irradiationlaser beam is obtained in the target region positioned 100 m away fromthe attachment lens 700.

(Scanning Lens 301)

-   -   double-aspheric surface    -   focal distance: 13.4912 mm    -   effective diameter: φ16 mm (aperture)    -   center thickness: 5 mm    -   refractive index: 1.517

(Attachment Lens 700)

-   -   incident side: toroidal surface/    -   outgoing side: spherical surface    -   focal distance: horizontal direction −23.0359 mm,        -   vertical direction −20.9278 mm    -   effective diameter: φ14.0 mm    -   center thickness: 1 mm    -   refractive index: 1.517

(Other)

-   -   distance between semiconductor laser and attachment lens: 52.81        mm    -   displacement amount of scanning lens: ±2 mm

It is assumed that the scanning lens 301 and the attachment lens 700 arearranged at the positions where the laser beam outgoing from theattachment lens 700 becomes the parallel beam in the horizontaldirection and the beam diameter (by the ray tracing) outgoing from theattachment lens 700 becomes a half of the beam diameter (also by the raytracing) incident to the scanning lens 301 in the horizontal directionwhen the center axes of the scanning lens 301 and attachment lens 700are aligned with each other, namely, when the scanning lens 301 islocated at the neutral position.

Each of FIGS. 10A to 10F, 11A to 11F, and 12A to 12C shows a beamintensity distribution (left) when the irradiation laser beam is swungby a predetermined angle in the horizontal direction by displacing thescanning lens 301 in the horizontal direction (Z-axis direction of FIG.1), a beam profile (middle) in the horizontal direction (horizontaldirection of the drawing) with respect to each beam intensitydistribution, and a beam profile (right) in the vertical direction(vertical direction of the drawing). The horizontal axis of the beamprofile is a distance from the beam center position (where the beamintensity is the highest), and the vertical axis is an intensity levelwhen the maximum intensity is set to 100. In the horizontal axis, thebeam center position is set to zero.

As can be seen from FIGS. 10A to 10F, 11A to 11F, and 12A to 12C, theincidence plane of the attachment lens 700 is formed in the toroidalsurface, which allows the irradiation laser beam to be formed in thebeam shape thinner than that of the first embodiment in the verticaldirection (Y-axis direction of FIG. 1). As a result, when compared withthe first embodiment, the vertical coverage of the irradiation laserbeam can be widened, and resolution can be enhanced in the horizontaldirection. In the case where the configuration is applied to thein-vehicle obstacle detection apparatus, as shown in FIG. 13B, thenumber of scanning stages (the number of blocks when the target regionis divided into matrixes) in the vertical direction can be decreased inthe target region, and the scanning resolution can be enhanced in thehorizontal direction. Therefore, the scanning control can be simplifiedand the detection accuracy can be improved in the horizontal direction.FIG. 13A shows the beam shape and the divided state of the target regionin the case where both the incidence plane and outgoing plane of theattachment lens 700 are formed in the spherical surface.

The attachment lens 700 suitable to the simulation conditions can beformed based on the following lens data. The lens data for the scanninglens 301 is similar to that of the simulation of the first embodiment,so that the description will be neglected.

(Attachment Lens 701)

a. Incidence Plane (Toroidal Surface)

curvature radius:

-   -   horizontal direction −60.16068895769 mm    -   vertical direction −40 mm        b. Outgoing Plane (Spherical Surface)

curvature radius 14.68847686175 mm

c. Material: glass/BK7 (refractive index=1.517)

According to the simulation conditions, the same wide angle action asthat of FIG. 6 can be realized.

As can be seen from FIGS. 10A to 10F, 11A to 11F, and 12A to 12C, aswith the first embodiment, the aberration is also generated in theirradiation laser beam according to the simulation conditions. In thecase where the simulation conditions are set to the optical system, thegeneration of the aberration becomes conspicuous from around theposition where the irradiation laser beam is scanned by about 15° fromthe neutral position (see FIGS. 11D to 11F), and the intensitydistribution of the irradiation laser beam becomes distorted in thehorizontal direction. When the scanning angle becomes about 20° (seeFIGS. 12A to 12C), the distortion of the intensity distribution becomessignificant. The distortion is also generated when the irradiation laserbeam is scanned in the vertical direction.

In order to decrease the distortion, it is necessary that the surface ofthe scanning lens 301 be set to be able to suppress the aberrationgenerated by the displacement of the scanning lens, or it is necessarythat a correction lens be separately arranged in an optical path tosuppress the aberration. On the apparatus side in which the beamirradiation apparatus of the second embodiment is mounted, when thedistortion of the intensity distribution becomes troublesome, it isnecessary that the distortion be decreased by such countermeasures.

In the in-vehicle beam irradiation apparatus, generally because thelaser-beam swing angle of about ±10 degrees is necessary in thehorizontal direction to monitor the front of the vehicle, unless theaberration is conspicuous when the swing angle is within the ±10degrees, there is generated no problem in the accuracy of theinter-vehicular distance detecting operation. Accordingly, in theoptical system designed according to the simulation conditions ismounted on the in-vehicle beam irradiation apparatus, the problem-freescanning operation can be realized without separately adding theaberration correction lens.

Thus, the shaping effect of the irradiation laser beam can be obtainedas well as the wide angle effect by adjusting the surface shape of theattachment lens 700. That is, both the swing-angle increased effect andthe scanning control simplification effect can simultaneously obtainedby the simple configuration.

Although the second embodiment of the invention described above, theinvention is not limited to the second embodiment, but variousmodifications could be made.

Although the incidence plane of the attachment lens 700 is formed in thetoroidal surface in the second embodiment, the incidence plane may beformed in the cylindrical surface in place of the toroidal surface. Inthis case, it is necessary that the orientation of the cylindricalsurface be adjusted such that the beam shape becomes thin in the desireddirection in the target region. It is also necessary that the surfaceshapes of the cylindrical surface (incidence plane) and sphericalsurface (outgoing plane) be designed such that the beam becomes thedesired size in the target region.

In the second embodiment, the beam shape is adjusted by devising theincidence plane of the attachment lens 700. Alternatively, a lens mayseparately be added to the optical system to adjust the beam shape.However, in this case, the number of components is increased and thecost is increased.

In the first and second embodiments, the lens actuator 300 is used asthe beam scanning means. Alternatively, as shown in FIG. 14, the beammay be scanned using a polygon mirror 900.

The polygon mirror 900 has a polygon in cross section, and a mirrorsurface is formed in each side face. The polygon mirror 900 is rotatedin the arrow direction in FIG. 14 by receiving drive force from a motor(not shown). When the side face is irradiated with the laser beam whilepolygon mirror 900 is rotated, the incidence angle of the laser beam ischanged with respect to each side face. Therefore, the laser beam(irradiation laser beam) reflected by the side face of the polygonmirror 900 is scanned in the rotational direction of the polygon mirror900.

In the polygon mirror 900, an inclination angle of each mirror surfaceis adjusted with respect to a rotating axis such that a scanning orbitin the horizontal direction is shifted by one block in the verticaldirection on the target region by transferring the incidence position ofthe laser beam from one mirror surface to the next mirror surface. Inthe case where the scanning orbit in the horizontal direction is locatedat the lowermost block position, when the incidence position of thelaser beam is transferred to the next mirror surface, the inclinationangle of the mirror surface is adjusted such that the scanning orbit inthe horizontal direction is shifted from the lowermost block position tothe uppermost block position.

The inclination angle of the mirror surface of the polygon mirror 900 isadjusted as described above, which allows the irradiation laser beam toscan the irradiation block shown in FIG. 13B step by step from the leftto the right according to the rotation of the polygon mirror 900.

In this case, the beam splitter 400, the servo lens 500, and a PSD 600can be neglected in FIG. 1. This is because the irradiation position ofthe laser beam can be detected from the rotational position of thepolygon mirror 900. In the configuration of FIG. 14, the rotationalposition of the polygon mirror 900 is sequentially detected based on arotating synchronous signal delivered from the motor, and theirradiation position of the irradiation laser beam is detected on thetarget region based on the detected rotational position.

Additionally, the laser beam can be scanned using a galvano-mirror and aMEMS (Micro Electro Mechanical Systems) mirror.

The beam irradiation apparatus of the invention can be applied to avariety of uses in addition to the in-vehicle use. The beam irradiationapparatus of the invention can be mounted on an image reading apparatusand the like in addition to the obstacle detection apparatus and thedistance detection apparatus.

Various changes and modifications of the above embodiments couldappropriately be made without departing from the technical thought shownin claims.

1. (canceled)
 2. (canceled)
 3. A beam irradiation apparatus comprising:a light source which emits a laser beam; a first lens which displaces atraveling direction of the laser beam emitted from the light sourcetoward a direction perpendicular to an optical axis of the laser beam;an actuator which drives the first lens; and a second lens which impartswide angle action to a swing angle of the optical axis, the swing anglebeing generated by displacing the first lens, wherein the second lensincludes a first lens surface which imparts the wide angle action to thelaser beam and a second lens surface which adjusts an outline of thelaser beam.
 4. A beam irradiation apparatus comprising: a light sourcewhich emits a laser beam; a first lens which displaces a travelingdirection of the laser beam emitted from the light source toward adirection perpendicular to an optical axis of the laser beam; anactuator which drives the first lens; and a second lens which impartswide angle action to a swing angle of the optical axis, the swing anglebeing generated by displacing the first lens, wherein the first lensconverges the laser beam smaller than a parallel beam, the second lensdiffuses the laser beam converged by the first lens into a substantiallyparallel state, and the second lens includes a first lens surface whichimparts the wide angle action to the laser beam and a second lenssurface which adjusts an outline of the laser beam.
 5. (canceled)
 6. Thebeam irradiation apparatus according to claim 3, wherein the second lenssurface imparts optical action to the laser beam such that the outlineof the laser beam becomes thin in one direction.
 7. The beam irradiationapparatus according to claim 4, wherein the second lens surface impartsoptical action to the laser beam such that the outline of the laser beambecomes thin in one direction.
 8. (canceled)
 9. A beam irradiationapparatus comprising: a light source which emits a laser beam; ascanning unit which scans the laser beam emitted from the light sourcewithin a target region; and an optical member which deforms an outlineof the laser beam in the target region so as to become thin in onedirection.
 10. The beam irradiation apparatus according to claim 9,wherein the scanning unit scans the laser beam in at least a horizontaldirection within the target region, and the optical member deforms theoutline of the laser beam in the target region so as to become thin in adirection perpendicular to the horizontal direction.
 11. The beamirradiation apparatus according to claim 9, wherein the scanning unitincludes a first lens and an actuator, the laser beam being incidentfrom the light source to the first lens, and the actuator driving thefirst lens in a direction perpendicular to an optical axis of the laserbeam, and the optical member includes a second lens which imparts focusaction to the laser beam, a focal distance in the horizontal directionbeing different from a focal distance in the vertical direction in thefocus action.
 12. The beam irradiation apparatus according to claim 9,wherein the scanning unit includes a first lens and a polygon mirror,the laser beam being incident from the light source to the first lens,and the polygon mirror having a plurality of reflection planes whichreflect the laser beam incident from the first lens, and the opticalmember includes a second lens which imparts focus action to the laserbeam, a focal distance in the horizontal direction being different froma focal distance in the vertical direction in the focus action.
 13. Thebeam irradiation apparatus according to claim 11 or 12, wherein thesecond lens includes a first and a second passing surfaces through whichthe laser beam passes, and the first passing surface is formed in a lenssurface which imparts the focus action to the laser beam, the focaldistance in the horizontal direction being different from the focaldistance in the vertical direction in the focus action.
 14. The beamirradiation apparatus according to claim 13, wherein the lens surface isa toroidal surface in which the focal distance in the horizontaldirection is different from the focal distance in the verticaldirection.